Field of the Invention
The invention relates to a resistive memory technology, and more particularly relates to a writing method for a resistive memory cell and a resistive memory using the writing method.
Description of Related Art
In the resistive random-access memory (RRAM) technology, the three operations: forming operation, set operation, and reset operation are three important steps to ensure the electrical property and the data retention of the resistive memory cell. When executing the set/reset operation, the input voltage needs being progressively increased many times to complete the operations. With respect to the RRAM device, completing the reset operation may increase the durability of the RRAM.
Generally, the resistive random-access memory may change a width of a filament path according to magnitude and polarity of an applied pulse voltage. For example, when a data logic 1 is written, the width of the filament path may be narrowed by applying RESET pulse so as to form a high resistance state. When a data logic 0 is written, the width of the filament path may be widened by applying SET pulse having a reversed polarity so as to forum a low resistance state. However, when the input voltage is continuously or inclinedly increased to execute the set operation or the reset operation of the resistive memory cell, the current which is originally corresponding to the high-current state of the resistive memory cell may be decreased or the current which is corresponding to the low-current state of the resistive memory cell is increased so as to cause errors in data stored in the resistive memory cell, this phenomenon is called complementary switching (CS) manifestation. In other words, when the set operation or the reset operation of the resistive memory cell is executed, if an excessive input voltage is provided, the resistive memory cell may become contrary to expectation.
On the other hand, after reset signal/set signal is inputted to the resistive memory cell several times, and if it is discovered that the resistive memory cell may be in between the high resistance state and the low resistance state continuously, this state of the resistive memory cell is called as a local high resistance state/local low resistance state. In order to change the state of the resistive memory cell to be different from the local high resistance state/local low resistance state, the input voltage of the resistive memory cell needs being further adjusted.
Therefore, when executing the operations of the resistive memory cell, how to prevent the input voltage in the process of progressively increasing from causing an excessive voltage to make the resistive memory cell generate the complementary switching manifestation and how to change the state of the resistive memory cell to be different from the local high resistance state/local low resistance state are important topics.